Tape laying and cutting system for fiber reinforced plastic manufacturing

ABSTRACT

This patent application focuses on the cutting, laying and impregnating the fiber tape using a tape laying and cutting head. The head contains a stationary or moving laser system with an in-situ mixing of resin and hardener, rollers (1,2) and a spreader (6) for pressing. The head enables manufacturing of small fiber reinforced parts avoiding the problems in manufacturing them.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. national phase of International ApplicationNo. PCT/FI2017/050251, filed Apr. 7, 2017, which claims priority toFinland Patent Application No. 20160087, filed Apr. 7, 2016, both ofwhich are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention concerns in general the technical field of materiallaying, machining and forming. More particularly, the invention concernsa laying device and a cutting device for fiber tapes.

BACKGROUND

Fiber reinforced plastic (FRP) parts are increasingly used in automotiveand aerospace industries due to their lightweight and high strength[1-3]. However, due to their high cost and specialized manufacturingprocesses, they have mainly been restricted to aerospace and high-endautomotive industries. The future of manufacturing for lightweightcomposite structures relies strongly on automation to bring down theoverall cost of FRP parts [4, 5].

Manufacturing of these FRP parts is gradually becoming automated using5-axis Automated Tape Laying (ATL) machines which are used formanufacturing big size parts. These ATL system employs a tape layinghead for laying down the carbon fiber prepreg tapes. Prepregs are fiberswhich have been pre-impregnated with a resin system (typically epoxy).In the process of laying, after each pass of laying tape, the tape iscut using an ultrasonic blade. However, these cutting systems are bulky,require frequent maintenance and blade replacements after an average ofabout 6000 cuts [6].

SUMMARY OF THE INVENTION

In this patent application, a new invention for a compact tape layingsystem for feeding, positioning, and impregnating the tape, with astationary or moving miniaturized cutting sub-system to cut the dryfiber tape is disclosed. The system is not limited to the width of thetape. The system has one or more rollers for guiding, feeding and layingthe tape, a stationary or moving cutter, a resin impregnation and mixingsystem and a spreading and compacting system for uniform and thoroughresin impregnation. The resin and hardener are mixed in-situ beforeimpregnating the tape. The system is able to move in X-Y-Z axes (linearmovements) and in A-B-C axes (rotating movements). Thus, fibers can belaid on a 3-dimensional surface over a mould of complex geometry. Thesystem is able to trim every layer of the FRP to an almost-finishedpart, reducing post-processing. Repeating the process layer upon layerin a controlled layup sequence and with a chosen fiber direction foreach layer, the desired parts are obtained.

BRIEF DESCRIPTION OF FIGURES

The embodiments of the invention are illustrated by way of example andnot by way of limitation, the figures of accompanying drawings.

FIG. 1 illustrates the laser cutting and laying head.

FIG. 2 illustrates the head moving directions.

DETAILED DESCRIPTION

In this patent application, an embodiment of a tape laying system forfeeding, positioning, impregnating and cutting a tape is presented. Alsoa method for manufacturing fiber reinforced plastic parts is presented.

The system of FIG. 1 comprises three major subsystems:

a. Tape rolling subsystem

b. Tape impregnation subsystem

c. Tape cutting subsystem

TABLE 1 The part No. and items in FIG. 1. Part No. Item 1 Upper roller 2Lower Roller 3 Gear train 4 Laser cutter 5 Resin mixer 6 Spreader 7 Tapepressing plate

TABLE 2 The head moving directions. X axis Fiber direction, and tapelaying passes direction Y axis Perpendicular direction to fiber (tapewidth) Z axis Perpendicular direction to fiber and tape width A, B and CRotation about X, Y and Z axis respectively

In this system, a tape laying head moves in planar motion (XZ plane)while placing one segment of tape on the mould for every pass beforecutting the tape and moving one tape width on Y direction. The planarmotion in XZ plane is only an example which helps to understand theconcept of this embodiment. The tape laying head of the system couldalso be moved in linear motion, in planar motion in any other plane orfollowing a path defined in a three-dimensional space. The tape-layinghead has a rolling system comprising one or more rollers. In anembodiment, the rolling system consists of two rollers, upper roller 1and lower roller 2 to keep the tape in tension. The upper roller 1 isidler and lower roller 2 is rotated by rotating a motor connected togear train 3 which in turn rotates the lower roller 2. The lower roller2 follows the XZ profile of the part, with the total head movement inthe X direction. The lower roller 2 is applying certain force towardsthe mould and can be rigid or elastic to ensure better placement offibers on complex moulds. In an embodiment the upper roller 1 can beomitted and the tension can be controlled with other means, e.g. bycontrolling the feeding or releasing of the tape from a roll. Tapepressing plate 7 ensures consistent contact of the tape and the lowerroller.

After laying a pass of tape, the tape is cut with a tape cuttingsub-system and the tape-laying head is shifted one tape width to adirection perpendicular to the direction of the previously laid tape. Inother words, the tape-laying head lays the tapes next to each other witheach pass until a defined surface is covered with the tape. After that asecond layer of tape can be laid on top of the first layer of tape.

Preferably, either the mould or the tape-laying head is rotated betweensuccessive layers to achieve crosswise direction of tapes betweensuccessive layers. The fiber orientation in each layer can be chosen byrotating the mould platform (rotates ±C direction) or the tape-layinghead itself. The head can be used for laying up on mould with free formsurfaces. Repeating the process and building layer by layer it formsdesired layup sequence and the parts. The term tape refers in thispatent application to a dry or lightly bounded spread fiber tow.Preferably a spread tow consisting of unidirectional fibers with orwithout a binder is used. The tape can also consist of unidirectionalfibers with crimps. In an embodiment, the binder component constitutesless than 10% of the total volume of the tape and preferably less than5% of the total volume. In an embodiment, the binder componentconstitutes less than 10% of the total mass of the tape and preferablyless than 5% of the total mass. The fibers of the tape can be any fibersthat are used as reinforcing fibers, such as carbon fiber, aramid fiber,glass fiber, or a combination of two or more types of fibers.

As the tape-laying head moves and lays the tape, an impregnationsubsystem impregnates the tape with a mixture of multi-component epoxythereby creating a multi-component layer consisting of the fibers of thetape and the epoxy impregnated into the tape. A two-component epoxyconsisting of a resin component and a hardener component is used as anexample but also other multi-component matrices can be used, such asthree-part methyl methacrylate adhesive system or a two-component epoxywith an accelerator component.

The impregnation subsystem comprises two or more containers for epoxycomponents, at least one container for each epoxy component. Thecomponents are pumped from said containers with pumps into a mixingunit. Preferably the number of pumps is equal to the number ofcontainers or equal to the number of epoxy components. For example, asystem using two-component epoxy, resin and hardener, can have total oftwo containers, one container for the resin component and one containerfor the hardener component and two pumps, one for each container. Thecomponents are preferably moved through tubing with the use of ametering pump (e.g. piston pump, peristaltic pump or screw pump). Thepumps are configured to pump the two or more components into a mixingunit which is preferably a static mixer 5. Mixing ratio of the epoxycomponents varies between component combinations and the pumps areconfigured to pump the components from the containers to the mixing unitaccording to the mixing ratio of said components. Pumping of the epoxycomponents in desired ratio to the static mixer 5 moves the epoxycomponents through the mixer and at the same time mixes the componentsthoroughly.

The mixed epoxy coming out from the mixer 5 can be applied on the tapethat has been laid and rolled against the mould. Typicallymulti-component epoxies have such a high viscosity that properimpregnation of the tape doesn't take place without assistance.Therefore the impregnation sub-system comprises a spreader or a spreadersystem which can have one or more functions. In an embodiment the mixedmulti-component epoxy coming out from the mixer 5 flows through a widespreading mechanism which spreads the epoxy and forms a layer of epoxyonto the tape covering most of the tape width, for example more than50%, more than 70% or more than 90% of the tape width. In anotherembodiment, the epoxy is applied directly from the static mixer on thetape. Once the epoxy has been applied on the tape, either directly orthrough a spreading mechanism, the epoxy is pressed into the tape inorder to fully impregnate the tape and to remove any air bubbles. Thepressing can be realized with a roller or flap 6 or a similar devicewhich exerts a force on the epoxy towards the tape.

At the end of each pass, the fiber tape is cut using a cutter of a tapecutting sub-system. Preferably a laser 4 is used where a laser beam,either converted into a stationary line, perpendicular to the fiberdirection, or with a focused beam moving perpendicular to the fiberdirection cuts the tape. With a stationary laser cutter, a uniform-powerdistribution line generating lens or lens system can be used forconverting the focused laser point into a line matching or exceeding thetape width. Preferably the width of this laser line is adjustable tomatch different tape widths. The adjustment can be realized e.g. bychanging the distance between the lens and the laser source.

A first aspect of the invention is a method of manufacturing fiberreinforced plastic parts. The method comprises using a tape rollingsystem to perform steps of placing a segment of a tape on a mould bymoving a tape-laying head of the tape rolling system in planar motion;mixing a mixture of resin and hardener; impregnating the tape with themixture of resin and hardener; distributing and compressing the mixtureof resin and hardener within the tape using a spreading mechanism of thetape rolling system; cutting the tape with a laser cutter of the taperolling system; and moving the tape laying head of the tape rollingsystem one tape width to a direction perpendicular to said planar motionand repeating the process again for multiple layers of different fiberorientation.

In an embodiment of the first aspect of the invention, said laser cutteris a stationary laser comprising a lens generating a uniform powerdistribution line. In an embodiment of the first aspect of theinvention, said laser cutter is a moving laser unit.

In an embodiment of the first aspect of the invention, said tape is acarbon fiber tape.

In an embodiment of the first aspect of the invention, said cutting stepis performed on a dry carbon fiber tape.

In an embodiment of the first aspect of the invention, said mixing stepand said impregnating step are performed in-situ.

In an embodiment of the first aspect of the invention, the methodfurther comprises a step of rotating the mould in relation to the tapelaying head between layers of tape for altering fiber orientationbetween layers.

A second aspect of the invention is a tape-laying system formanufacturing fiber reinforced plastic parts. The system comprises atape rolling sub-system comprising a movable tape-laying head having arotatable roller for tensioning and placing a tape; a tape impregnationsubsystem comprising means for mixing resin and hardener with each otherand a spreader for impregnating the tape with said mixture; and acutting sub-system comprising a laser cutter configured to cut the tapewith a laser beam.

In an embodiment of the second aspect of the invention, said cuttingsub-system comprises a lens configured to convert said laser beam into astationary line perpendicular to the fiber direction.

In an embodiment of the second aspect of the invention, said cuttingsubsystem is configured to cut the tape using a focused beam movingperpendicular to a direction of fibers in the tape.

A third aspect of the invention is a method of manufacturing fiberreinforced plastic parts. The method comprises using a tape rollingsystem to perform steps of: placing a segment of a tape on a mould bymoving a tape-laying head of the tape rolling system; providingcomponents of a multi-component epoxy in defined ratios to a mixer;mixing a mixture of multi-component epoxy with the mixer; spreading themixture of multi-component epoxy on the placed segment of the tape;impregnating the mixture of multi-component epoxy into the tape; cuttingthe tape with a cutter of the tape rolling system; and moving thetape-laying head of the tape rolling system one tape width to adirection perpendicular to fiber direction of the placed tape segment.

In an embodiment of the third aspect of the invention, said cutter is astationary laser cutter comprising a laser source and a lens generatinga uniform power distribution line.

In an embodiment of the third aspect of the invention, said cutter is amoving laser unit comprising a laser source.

In an embodiment of the third aspect of the invention, said tape is aspread tow of fibers, wherein the fibers are selected from the followingfibers: carbon fiber, aramid fiber and glass fiber.

In an embodiment of the third aspect of the invention, said cutting stepis performed on a dry portion of the tape.

In an embodiment of the third aspect of the invention, said mixing stepand said impregnating step are performed in-situ.

In an embodiment of the third aspect of the invention, the methodfurther comprises a step of rotating the mould in relation to the tapelaying head between layers of tape for altering fiber orientationbetween layers.

A fourth aspect of the invention is a tape-laying system formanufacturing fiber reinforced plastic parts. The system comprises atape rolling sub-system comprising a movable tape-laying head having oneor more rotatable rollers 1, 2 for tensioning and placing a tape; a tapeimpregnation subsystem comprising a container for each component of amulti-component epoxy, a plurality of pumps for pumping said componentsto a mixer 5 for mixing components of a multi-component epoxy with eachother, and a spreader 6 for impregnating the tape with said mixture; anda cutting sub-system comprising a cutter 4 configured to cut the tape.

In an embodiment of the fourth aspect of the invention, said cuttingsub-system is a laser cutter 4 comprising a laser source and a lensconfigured to convert a laser beam from the laser source into astationary line perpendicular to a fiber direction of the tape.

In an embodiment of the fourth aspect of the invention, said cuttingsub-system is a laser cutter 4 comprising a laser source configured tocut the tape using a focused beam moving perpendicular to a direction offibers in the tape.

In an embodiment of the fourth aspect of the invention, said cuttingsub-system 4 is located between said tape rolling subsystem and saidtape impregnation subsystem for cutting a dry, non-impregnated, tape.

The system enables manufacturing of small fiber reinforced parts withouthuman intervention. Thus, consistent quality can be achieved andmanufacturing costs can be reduced. In addition, the system avoids humanexposure to carcinogenic material (epoxy resins are typically used)while manufacturing FRP parts thus reducing the health hazard to thelaborer. The system provides manufacturing freedom as of additivemanufacturing with strength of FRP composites, allowing manufacturing ofhigh strength quality parts with ease.

REFERENCES

-   1. Mills, A., Automation of carbon fibre preform manufacture for    affordable aerospace applications. Composites Part A: Applied    Science and Manufacturing, 2001. 32(7): p. 955-962.-   2. Wisbey, J. D., Multi-tow fiber placement machine with full band    width clamp, cut, and restart capability. 1990, Google patents.-   3. M, V. M., U.S. Pat. No. 5,110,395. 2016.-   4. Prüß, H. and T. Vietor, Design for fiber-reinforced additive    manufacturing. Journal of Mechanical Design, 2015. 137(11): p.    111409.-   5. COMBINING ADDITIVE MANUFACTURING WITH FRP COMPOSITES: DESIGN    POTENTIALS. 2016.-   6. Composite Materials—Science and Engineering|Krishan K.    Chawla|Springer. 2016.

The invention claimed is:
 1. A method performed by a tape-laying system,the method comprising: pressing a segment of a tape onto a mold using aroller; applying an epoxy on the segment of the tape using a mixer afterpressing the segment of the tape onto the mold using the roller;impregnating the epoxy into the segment of the tape; and cutting thetape at a position that is between the mixer and the roller.
 2. Themethod of claim 1, wherein cutting the tape comprises cutting the tapeusing a laser.
 3. The method of claim 1, wherein said tape is a spreadtow of fibers, selected from one or more of carbon fiber, aramid fiber,or glass fiber.
 4. The method of claim 1, further comprising mixing afirst component and a second component to form the epoxy, wherein themixing and the impregnating are performed in-situ.
 5. The method ofclaim 1, further comprising: rotating the mold after impregnating theepoxy into the segment of the tape; and pressing a segment of a secondtape onto the mold after rotating the mold.
 6. The method of claim 1,further comprising: moving a tape-laying head of the tape-laying systemin a first direction along the mold while pressing the segment of thetape, applying the epoxy, and impregnating the epoxy; and moving thetape-laying head in a second direction along the mold that isperpendicular to the first direction after impregnating the epoxy intothe segment of the tape.
 7. A tape-laying system comprising: a rollerconfigured for pressing a segment of a tape onto a mold; a mixerconfigured for applying an epoxy on the segment of the tape afterpressing the segment of the tape onto the mold using the roller; and aspreader configured for impregnating the epoxy into the segment of thetape; and a cutter configured to cut the tape at a position that isbetween the mixer and the roller.
 8. The tape-laying system of claim 7,wherein the tape-laying system is configured to apply the tape to themold along a first direction, and wherein the cutter comprises a laserconfigured to cut the tape perpendicularly to the first direction. 9.The tape-laying system of claim 7, wherein said cutter is locatedbetween said roller and said spreader.
 10. The tape-laying system ofclaim 7, wherein the mixer is between the spreader and the cutter.